1. Field of the Invention
The present invention concerns a novel application of fluidised bed technology for the recovery or extraction of materials such as metals from wastes or other sources. More particularly, metals in particulate form may be recovered, primarily but not exclusively as oxides, from material which includes substantial quantities of matter which is combustible or otherwise degradable, such as spent catalyst materials.
2. Background of the Art
The invention has been developed mainly in connection with the recovery of nickel (as an oxide) from spent hydrogenation catalysts, but also has other applications as will be evident from the following description.
Hydrogenation catalysts as supplied commercially for the hardening of fats and oils comprise finely divided nickel on a siliceous carrier formed into pellets with a hard fat for use with a liquid or molten state system. In use, the fat dissolves or melts and the nickel-on-carrier particles are dispersed throughout the system. The used catalyst particles are then separated by filtration into a slurry or sludge containing organic matter. This material may be returned to the reaction vessel and re-used several times, but after a period of use, it becomes spent and is removed from the system entirely.
A similar process is adopted for other hydrogenation processes, such as of nitriles to form amines where a `Raney` nickel catalyst, a finely divided sponge nickel stored under inert gas or water, is introduced and dispersed through a system and removed contaminated with organic matter after its reaction is complete.